Geared-turbine system



C. A. PARSONS, S. S. COOK AND L. M. DOUGLAS.

GEARED TURBINE SYSTEM.

APPLICATION FILED AUG-11,19l9.

Pat-mm, May M), 1921.

2 SHEETSSHEET I C. A. PARSONS, S S COOK AND L M. DOUGLAS.

GEARED TURBINE svsmw.

APJLICATION FILED AUG.1|, I919. g y y g g May ML 1921.

2 SHEETS*SHEET 2.

k LT 1W 71 60 715,, A m 27 (LWQ/gLa 62 j UNITED STATES PATENT OFFICE.

CHARLES ALGEBNON PARSONS, STANLEY SMITH COOK, AND LOUIS MORTIMERDOUGLAS, OF NEWCASTLE-UPON-TYNE, ENGLAND; SAID COOK AND SAID MUGIIASASSIGNOBS T0 SAID PARSONS.

GEABED-T'URBINE SYSTEM.

Specification of Letters Patent.

original application filed October 31, 1918, Serial No. 260,552. Dividedand this application filed August 11, 1919. Serial No. 316,921.

To all whom it may concern:

Be it known that we, Cmnnns Anonnnon Parsons, STANLEY SMITH Coon, andLows MORTIMER lDoUcLAs, all subjects of the King of Great Britain andIreland, all residing at Heaton Works, Newcastle-upon-Tyne, in thecounty of Northumberland, England, have invented certain new and usefulTmprovements in Geared-Turbine Systems, of which the followingis aspecification.

The present invention relates to geared turbine systems, in which aturbine transmits power through a double helical gear train.

As usually constructed turbines are provided with a thrust or adjustingblock of the pivoted or ordinary type for the purpose of retaining thelongitudinal position of the rotor relative to the stator. When such aturbine is driving a pinion having double helical gear teeth, it isnecessary to provide a sliding coupling between the pinion and theturblne rotor, in order that each may take up its own longitudinalposition, that of the turbine rotor being controlled by the adjustingblock and that of the pinion by the intermeshing gear teeth.

Thrust bloclis of the ordinary fixed collar type are frequently thecause of considerable trouble in operation, and pivoted thrust blocks,although they are practically free from running troubles if properlyconstructed, are somewhat expensive to manufacture. it is, therefore,desirable to dispense with adjusting blocks so far as is possible.

Sliding couplings have both the above mentioned disadvantagesthey arevery expensive to manufacture for high power, high speed shafts and theyare frequently the cause of considerable trouble in running.

The object of the present invention is to overcome these difiiculties.

The invention consists in a geared turbine system in attaching theturbine rotor directly to the pinion shaft with a fixed coupling andcausing the pressure per unit length of both of the intermeshing doublehelical pinions to be uniform.

The invention further consists in increasing the length of one of thehelices of the double helical pinions relatively to the other so as tobalance the thrust exerted by the turbine and insure a substantiallyuniform distribution of pressure across the pinion teeth. 1

The invention also consists in designing the turbine in such a mannerthat the difference in width of the helices required to balance the endthrust is that which will cause the best distribution of forcespossible, so far as deflection due to torque of the pinions isconcerned.

The invention also consists proved geared turbine arrangementshereinafter described.

Referring to the accompanying drawlugs:-

Figure 1 shows the application of the invention to an impulse reactionturbine.

Fig. 2 is a diagram illustrating the most desirable proportion of thegearing.

Fig. 3 il ustrates the application of the invention to a low pressureunbalanced turbins; and I Fig. 4 illustrates its application to doublereduction gearing.

The invention is applicable to a geared turbine system employing anykind of turbine in which there is an axial thrust along the shaft.

In the form of the invention illustrated in Fig. 1, an impulse-reactionturbine r c is employed in which the low pressure reaction portion 8 isunbalanced and the turbine consequently has an axial thrust in thedirection of the pinion. In order to obtain as far as possible a uniformdistribution of pressure across the pinion teeth, one of the helices cof the gear is made wider than the other d. This increased length of oneof the helices is necessary in viewv of the fact that the torquetransmitted by each of two equal and oppositely inclined helices isproportional to the longitudinal forces between the teeth and thedifierence between the longitudinal forces in this case will be equal tothe turbine thrust. With gears so proportioned, an added advantage isobtained from the fact that the deflections of the pinion due to itstorque are more nearly equal on the two helioes -of the pinion, when thein the im-' which assuming that the drive is from the left hand end andthat the pressure on the teeth per unit of length is uniform, theordinates of the curve represent torsional deflection or twist at pointsalong the pinion. It is desirable that the maximum twist on each helixshould be made as low as possible, and the lengths e,, e, of the helicesare therefore so chosen that the deflections d (1, are equal. Thisinequality of helix width results in an end thrust which is arranged tovbe balanced by that of the turbine. Fig. 3 illustrates the modificationin which a low pressure unbalanced turbine t with unequal helices c andd is employed.

As in the previous case, an astern turbine u is incorporated with themain turbine and the thrust of the mam turbine is of such a directionand magnitude that it is balancedroduced by the unequal heli-.

by the thrust when power is being transcal gear whee s mitted throughthem.

Fi 4 shows a double reduction gear in whic both primary gears 20,21, 22,23, and secondary gears 24, 25 26, 27, have the complementary helices ofthat the steam thrust of the turbine 28 is carried by the gears withapproximately uniform distribution of. pressure on the teeth of thelatter. The proportionate difference betweenthe widths of the primarygears 20, 21, is much greater than that between the widths of thesecondary gears 24, 25, on account of the relatively smaller total forceon the teeth of the former.

In this installation, andall those in which the gears receive axialthrust from the turbine, the arran ment is preferably, but notnecessarily, suc op osed to the propeller thrust.

t will be seen that in cases in which the turbine is to be exactly steambalanced and also in cases in which the unbalanced thrust is to be adetermined quantity to suit the gear proportions adopted, means may beadopted for adjusting exactly the steam balance or thrust after theconstruction of the turbines. should be permanent and may consist, in

the case of a dummy piston,'in connecting unequal widths, so.

that the turbine thrust is These means of adjustment the leak-ofichamber behind the piston to a suitable stage of the turbine systemwhich will give a back pressure insuring correct balance or thrust. Asan area of the dummy leakage escape passage may be adjusted, or theblades may be slightly opened or closedor partly bafiled by a coveringplate.

alternative, the.

Though a fixed rigid flanged couplingis I mentioned and shown on thedrawings any coupling may be used which gives longitudinal and angularrigidity between the two elements.

Having now described our invention, what we claim as new and desire tosecure by Letters Patent is 1. In a geared turbine system, a rotor, ashaft co-axial with the rotor and connected to it by a rigid coupling, adouble helical inion mounted on said shaft, the oppositely inclinedparts of said pinion being-of unequal length whereby the pressure perunit length of tooth of the intermeshing double helical pinion will beuniform, substantially as described. 2. Ina ared turbine system a rotor,a shaft coaxial with the rotor and connected to it by a rigid coupling,a doublehelical pinion mounted on said shaft, the oppositely inclinedparts of said pinion being of un-' equal length whereby the longitudinalthrust of the turbine rotoris balanced by an equal. and oppositelongitudinal thrust of the double helical pinion when power is beingtransmitted through said pinion, substantially as described.

3. In a geared turbine system as set forth in claim 2, a double helicalpinion divided into parts having oppositely inclined teeth and of such alength that when power is transmitted through said pinion the totaltorsional deflections across the helices are equal. v

4. In a geared turbine system as set forth in claim 1, primary gearsmeshing with the double helical pinion, and of a width corresponding tothat of the arts of said double helical pinion with whlch they mesh andsecondary gearing associated with each of the primary gears, saidsecondary gearing including members coaxial with the primary gears andhaving complementary helices of unequal widths, substantially asdescribed.

In testimony whereof we have signed our names to this s ecification.

OHARLE ALGERNON PARSONS. STANLEY SMITH COOK. LOUIS MORTIMER DOUGLAS.

